Replacing Suzuki Cams and Street vs. Track Tire Pressure | Ask the Geek

Suzuki SV and TL Models
I have been trying for some time now to find out if I can replace my Suzuki SV1000 cams with TL1000R cams and if there is any performance to be gained by doing this. I cannot get any information from Suzuki, not even cam duration/timing figures on either model.
Mario Pin
via SRmail

Mark Junge of Vesrah Suzuki (, 262-878-5930) built some fast SV1000s that Tray Batey used to win quite a few Suzuki cup races, and knows a few tricks to improve the papa SV. According to Junge, the TL cams alone will not work with the SV; you would have to use the complete TL heads as well, and even the TL pistons for best performance. There are other options to improve your bike’s performance: “The best modification we did was build a ram air box for the SV,” says Junge. “It completely changed the bike.” Unfortunately, few — if any — companies offer a true ram air kit for the SV, so you’d most likely have to cobble something together on your own. You could also look at improving your SV’s chassis: “The TL chassis was weak,” notes Junge, “and the SV really handled well once you installed good shock and fork components."

Street vs. Track Tire Pressure
While on a basic level I understand the reason to carry lower tire pressure during track/race events compared to street riding, but what are the pros and cons of doing so? Also, what occurs besides quicker tread wear if lower pressures are used on the street? Any "rules of thumb" for such practices? I'm also curious why in a track situation you'd have more front tire pressure than rear tire pressure when tire manufacturers recommend more rear tire pressure than front tire pressure: usually around 32-34 psi front and 42 psi rear for street applications.
via the SR forum

Firstly, it’s important to note the differences between track-oriented race tires and street tires. DOT race tires and slicks have specific tread compounds and constructions intended for use on the track; things like wear and stability are less important than all-out grip under controlled conditions. Street tires are designed with a different agenda: traction, stability and wear are all important, but additionally they must work in a wide range of conditions, including temperature extremes, dry and wet pavement, and with the additional load of a passenger and luggage. Typically, when riding solo on the street we use the front pressure you state but a lower rear pressure — around 36 psi compared to 42 psi. The manufacturers commonly list around 42 psi for rear pressure because they must take into account the additional load of a passenger and luggage. Certainly, on a sport-touring bike or with a passenger we will use accordingly higher tire pressures.

Using lower pressures on the track — 30 psi front and rear is a good starting point for street tires on the track — provides a larger contact patch and more grip, generally at the expense of wear. A lower pressure will also give more compliance over bumps while leaned over. The difference in pressure change between the front and rear tires is partly due to their different size and partly due to the different loads they encounter in each venue. Note that proper DOT race tires and slicks almost always require even less pressure in the rear tire; their tread compounds and constructions are designed specifically to work best in a narrow range of conditions at that lower, optimum pressure. A street tire, designed and built to work over a much wider range of parameters, requires more support from higher pressure even on the track.

As noted, wear is the greatest factor when using those low pressures on the street, but there are other considerations. A tire with less air will deform more easily, and straight-line stability will suffer. That additional deformation can lead to overheating in extreme cases, especially on a long freeway ride, leading to even more wear. SR

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